1. Numerical Simulation of Effective Heat Recapture Ammonia Pyrolysis System for Hydrogen Energy.
- Author
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Lim, Jian Tiong, Ng, Eddie Yin-Kwee, Saeedipour, Hamid, and Lee, Hiang Kwee
- Subjects
HEAT exchanger efficiency ,HEAT convection ,PYROLYSIS ,HYDROGEN production ,WASTE gases ,ACTIVATION energy ,NITROGEN ,HYDROGEN as fuel - Abstract
This paper proposes a solution to address the challenges of high storage and transport costs associated with using hydrogen ( H 2 ) as an energy source. It suggests utilizing ammonia ( N H 3 ) as a hydrogen carrier to produce H 2 onsite for hydrogen gas turbines. N H 3 offers higher volumetric hydrogen density compared to liquid H 2 , potentially reducing shipping costs by 40%. The process involves N H 3 pyrolysis, which utilizes the heat waste from exhaust gas generated by gas turbines to produce H 2 and nitrogen ( N 2 ). Numerical simulations were conducted to design and understand the behaviour of the heat recapture N H 3 decomposition system. The design considerations included the concept of the number of transfer units and heat exchanger efficiency, achieving a heat recapture system efficiency of up to 91%. The simulation of N H 3 decomposition was performed using ANSYS, a commercial simulation software, considering wall surface reactions, turbulent flow, and chemical reaction. Parameters such as activation energy and pre-exponential factor were provided by a study utilizing a nickel wire for N H 3 decomposition experiments. The conversion of N H 3 reached up to 94% via a nickel-based catalyst within a temperature range of 823 K to 923 K which is the exhaust gas temperature range. Various factors were considered to compare the efficiency of the system, including the mass flow of N H 3 , operating gauge pressure, mass flow of exhaust gas, among others. Result showed that pressure would not affect the conversion of N H 3 at temperatures above 800 K, thus a lower amount of energy is required for a compression purpose in this approach. The conversion is maintained at 94% to 97% when lower activation energy is applied via a ruthenium-based catalyst. Overall, this study showed the feasibility of utilizing convective heat transfer from exhaust gas in hydrogen production by N H 3 pyrolysis, and this will further enhance the development of N H 3 as the potential H 2 carrier for onsite production in hydrogen power generation. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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